This invention relates to a moving coil transducer in which the moving coil is wound of multiple strand or litz wire.
In the prior art, in a moving coil transducer such as a loudspeaker, the voice-coil is wound of a solid wire, which is then connected to intermediate conductors somewhere on the moving parts of the mechanical system. The moving parts usually consist of a voice coil, diaphragm, and some sort of suspension. The intermediate conductor is then used to make the physical and electrical connections either to the input terminals of the unit or to some intermediate point on the fixed structure. The connections made between the intermediate and coil wires are usually soldered and fastened to the moving system in some manner such as gluing. Rising labor costs and the high degree of skill necessary to perform this task properly are disadvantages of such a construction. Such a construction also requires close inspection to insure against faulty solder joints and damage to the diaphragm or suspension.
The intermediate conductor used in such prior art constructions is usually braided or stranded and of a larger wire gauge than the solid voice-coil wire. The intent in using a heavier conductor which is braided or stranded is to increase its resistance to flexural strain which could lead to work hardening and consequent breakage. In that respect, such a design is effective. However, the high mass of the intermediate conductor and that of the solder and associated materials which remain on the moving parts increases the moving mass of the system. The increase in mass makes no contribution to the surface area or structural integrity of the diaphragm and tends to increase distortion and degrade the performance of the unit. Some designs call for a total moving mass which is very small and diaphragms which are thin and somewhat pliant. These moving systems may be required to accelerate and decelerate extremely fast. The use of intermediate conductors in such a system increases mass and mechanical resistance. This will reduce the ratio of force to mass, causing a reduction in efficiency and reduced ability to operate at high frequencies. The excess mass may also cause high distortion in light weight, flexible diaphragms through premature nodal and harmonic break-up.
Another prior art method that has been employed in the manufacture of high frequency moving coil transducers involves the continuation of the solid voice coil wires from the coil to the input terminals where the electrical and physical connections are made. This technique usually involves special wire geometries which are intended to reduce the effects of work hardening and flexural strain on that portion of the wire which extends from a fixed position on the moving part to a fixed position on the non-moving part of the mechanical system. Often, the restrictions of space within the transducer unit inhibit both the design and feasible implementation of wire configurations which are effective in reducing the strain to acceptable limits. Even when used in the best contemporary designs, the solid wire is inherently prone to breakage due to concentrated stress at its fixed points.